The invention relates to wireless data communication, and more specifically, to simultaneous data and voice communication via a wireless communication system.
Wireless communication systems are constantly evolving. System designers are continually developing greater numbers of features for both service providers and users. Cellular based phone systems, for example, have advanced tremendously in recent years. Among various features available in the wireless phone systems, Short Message Service (SMS) is one of the most popular functions. SMS is a point to point, or point to multi-point service that enables users to exchange text messages over a communications network. Receipt notification, wherein the receiving station returns an acknowledgement, indicating that the message has been delivered is included in the service. SMS communication, however, is not “real time”, that is, messages are exchanged independently of each other, and as such, SMS communication does not require the establishment of a simultaneously contiguous end-to-end traffic path. A typical SMS system includes user terminals as the initiators or final destinations for messages, a Short Message Service Center (SMSC), which serves as a relay for messages among terminals throughout the network, and the network itself serving as the communications medium for the messages. The Short Message Transfer Protocol (SMTP), including various lower layer protocols, manages the transfer of messages among terminals.
An SMS message is initially sent by an SMS capable terminal (i.e. a mobile station) via the communications network, and is received and stored by the SMSC. The SMSC determines if the intended destination of the SMS message is available to the network, and if so, the message is then sent to that destination. Whenever an SMS capable terminal is registered to a network, it is capable of exchanging SMS messages, even when the terminal is engaged in a voice or data call. If the intended destination is not available, or does not acknowledge delivery, the SMSC may then initiate any number of message handling routines including re-transmitting the message at periodic intervals or even discarding the message.
Enhanced Messaging Service (EMS) is an application-level extension to SMS for cellular phones available on Global Systems for Mobile communications (GSM), Time Division Multiple Access (TDMA), and Code Division Multiple Access (CDMA) networks. An EMS-enabled mobile phone can send and receive messages that have special text formatting (such as bold or italic), animations, pictures, icons, sound effects, and special ring tones. EMS messages that are sent to devices that do not support EMS will be treated as SMS transmissions. The EMS standard was defined by 3GPP (3rd Generation Partnership Project), the same standardization body from which the worldwide success of GSM and the standardization of SMS originated. It is a completely open standard that may be supported by any manufacturer in the interests of interoperability between consumers. The EMS has been standardized by extending the use of User Data Header (UDH) in the SMS standard. FIG. 1 shows an EMS message schema, wherein all the media is stored in the UDH, while the text is stored in the normal text area of the short message.